<table>
  <thead>
    <tr>
      <th>Name</th>
      <th>Size in bytes</th>
      <th>Default value</th>
      <th>Comment</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>Protocol</td>
      <td>1</td>
      <td>0xC5</td>
      <td>-</td>
    </tr>
    <tr>
      <td>Size</td>
      <td>4</td>
      <td>-</td>
      <td>The size of the message in bytes not including
the header and size ﬁelds
</td>
    </tr>
    <tr>
      <td>Type</td>
      <td>1</td>
      <td>0x87</td>
      <td>The value of the OP_SECIDENTSTATE opcode</td>
    </tr>
    <tr>
      <td>Operation</td>
      <td>1</td>
      <td>2</td>
      <td>Indicates whether a public key and a signature are needed (2) or that only a signature is needed (1)</td>
    </tr>
    <tr>
      <td>Challenge</td>
      <td>4</td>
      <td>NA</td>
      <td>A random word for the peer to sign</td>
    </tr>
  </tbody>
</table>